U.S. patent number 4,386,893 [Application Number 06/260,142] was granted by the patent office on 1983-06-07 for gear pump or motor with a shaftless gear.
This patent grant is currently assigned to Deere & Company. Invention is credited to Herbert J. Hauser, Jr..
United States Patent |
4,386,893 |
Hauser, Jr. |
June 7, 1983 |
**Please see images for:
( Certificate of Correction ) ** |
Gear pump or motor with a shaftless gear
Abstract
In a gear pump or motor having a housing and at least two
intermeshing gears, one of the gears being fixed to a rotatable
shaft and the other being a shaftless gear having a plurality of
gear teeth rotatable on a film of fluid in close proximity to an
interior surface of the housing, the improvement being a unique
tooth profile on the shaftless gear. Each gear tooth on the
shaftless gear has a thick top land, preferably at least twice as
thick as the top land on each gear tooth on the gear fixed to the
rotatable shaft. This particular intermeshing gear tooth
configuration increases the bearing surface of the shaftless gear
on the film of fluid within the interior of the housing to better
support the shaftless gear and thereby reduce frictional wear.
Inventors: |
Hauser, Jr.; Herbert J.
(Waterloo, IA) |
Assignee: |
Deere & Company (Moline,
IL)
|
Family
ID: |
22987941 |
Appl.
No.: |
06/260,142 |
Filed: |
May 4, 1981 |
Current U.S.
Class: |
418/191;
418/196 |
Current CPC
Class: |
F04C
2/084 (20130101) |
Current International
Class: |
F04C
2/00 (20060101); F04C 2/08 (20060101); F01C
001/20 (); F03C 002/08 (); F04C 002/20 () |
Field of
Search: |
;418/190,191,196,199,200
;74/413,414,421R,460,462 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Vrablik; John J.
Claims
I claim:
1. In a gear pump or motor having a housing and at least two
intermeshing gears, one of said gears fixed to a rotatable shaft
and having a plurality of gear teeth and the other being a
shaftless gear having a plurality of gear teeth rotatable on a film
or fluid in close proximity to an interior surface of said housing,
the improvement comprising top lands having a narrow thickness on
said gear teeth of said gear fixed to said shaft and top lands
having a wider thickness on said gear teeth of said shaftless gear
for increasing the bearing surface of said shaftless gear on said
film of fluid within said housing.
2. In a gear pump or motor having a housing and at least two
intermeshing gears, one of said gears fixed to a rotatable shaft
and having a plurality of gear teeth with top lands and the other
being a shaftless gear having a plurality of gear teeth with top
lands rotatable on a film of fluid in close proximity to an
interior surface of said housing, the improvement comprising:
said top lands of said gear teeth on said shaftless gear having a
combined thickness equal to between about 30 and 50 percent of the
circumference of said shaftless gear and having a wider thickness
than said top lands of said gear fixed to said rotatable shaft for
providing a large bearing surface for said shaftless gear on said
film of fluid within said housing.
3. An improvement according to claim 2 in which said combined
thickness of all of the top lands of the gear teeth on said
shaftless gear is approximately 40 percent of the circumference of
said shaftless gear.
4. An improvement according to claim 2 in which the top lands of
said gear teeth on said shaftless gear are at least twice as thick
as the top lands of said gear teeth of said gear fixed to said
rotatable shaft.
5. In a gear pump or motor having a housing enclosing at least two
intermeshing gears, each gear having a plurality of gear teeth with
an involute tooth profile and top lands, one of said gears being
fixed to a rotatable shaft and the other being a shaftless gear
rotatable on a film of fluid in close proximity to an interior
surface of said housing, the improvement comprising: said top lands
on the gear teeth of said shaftless gear being approximately twice
as thick as the top lands on the gear teeth of said gear fixed to
said rotatable shaft and further having edge chamfers of between
about 10 and 30 degrees formed on each side of said top land of
each gear tooth and aligned parallel to the central axis of said
shaftless gear.
6. An improvement according to claim 5 in which each gear tooth on
said shaftless gear contains an end chamfer of between about 30 and
50 degrees on each top land which is aligned perpendicular to said
edge chamfers, all of said end chamfers being located on one side
of said shaftless gear for facilitating assembly of said shaftless
gear in an interior bore of said housing.
7. An improvement according to claim 6 in which two or more
shaftless gears mesh with a gear fixed to a rotatable shaft.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an improved gear pump or motor with a
shaftless gear and more particularly to an improved gear pump or
motor with a shaftless gear having a plurality of gear teeth with a
unique tooth profile intermeshing with a gear fixed to a rotatable
shaft.
2. Description of the Prior Art
Much effort has been spent in designing gear pumps or motors with a
shaftless gear. Such pumps and motors reduce the assembly cost,
eliminate some of the manufacturing problems associated with
maintaining close tolerances between the gears and the interior of
the housing, and of course they reduce the number of needed parts
by eliminating at least one gear shaft and its corresponding
bearings. Three such gear pumps or motors are described in the
following U.S. Pat. Nos. 2,626,570, issued to Armington et al in
January, 1953; 3,120,190, issued to Schmitter et al in February,
1964; and 3,286,643, issued to Andrews et al in November, 1966. The
major problem with these kinds of pumps or motors is that the
shaftless gear is inadequately supported within the housing and
therefore tends to rub and wear against an interior surface of the
housing. With increased wear, the shaftless gear moves further and
further away from the fixed gear. This allows an increased volume
of fluid to remain in the gear troughs of the intermeshing gears
instead of being forced out of the pump or motor. After the
efficiency of the pump or motor drops below a predetermined value,
it has to be replaced. By reducing the wear of the gear teeth and
the internal surface of the housing, the life of the pump or motor
can be extended thereby necessitating less frequent replacement
resulting in a cost savings to the owner.
Now an improvement for a gear pump or motor with a shaftless gear
has been invented which increases its life expectancy by utilizing
a shaftless gear having a unique tooth profile.
SUMMARY OF THE INVENTION
Briefly, this invention relates to an improved gear pump or motor
having a housing with at least two intermeshing gears, one of the
gears being fixed to a rotatable shaft while the other gear is a
shaftless gear rotatable in close proximity to an interior surface
of the housing. The improvement resides in the overall shape and
size of the gear teeth on the shaftless gear. Each gear tooth on
the shaftless gear has a thick top land, preferably at least twice
as thick as the top land of each gear tooth on the gear fixed to
the rotatable shaft. Furthermore, the combined thickness of all of
the top lands on the gear teeth of the shaftless gear equal
approximately 40 percent of the circumference of the shaftless
gear. This particular tooth configuration increases the bearing
surface of the shaftless gear on a film of fluid within the
interior of the housing to better support the shaftless gear and
thereby reduce frictional wear.
The general object of this invention is to provide an improved gear
pump or motor having a shaftless gear which has a longer life
expectancy because the frictional wear between the shaftless gear
and the interior of the housing is reduced. A more specific object
of this invnetion is to provide an improved gear pump or motor
having a housing with at least two intermeshing gears, one gear
being fixed to a rotatable shaft and the other being a shaftless
gear having a plurality of gear teeth with thick top lands, the
combined thickness of said top lands equaling approximately 40
percent of the circumference of the shaftless gear.
Another object of this invention is to provide an improved gear
pump or motor with a shaftless gear wherein the profile of the gear
teeth on the shaftless gear are configured to provide increase
support to the shaftless gear approximately equivalent to the
support provided by a standard size gear shaft.
Other objects and advantages of the present invention will become
more apparent to those skilled in the art in view of the following
description and the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional view of an improved gear pump or motor
having a housing with a pair of intermeshing gears, one gear being
a shaftless gear having a plurality of gear teeth with a unique
tooth profile for better supporting the shaftless gear within the
housing.
FIG. 2 is an enlarged perspective view of a single gear tooth
having the improved profile with two chamfered edges and a
chamfered end.
FIG. 3 is an alternative configuration to FIG. 1 showing two
shaftless gears intermeshing with a gear fixed to a rotatable
shaft.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to FIG. 1, a gear pump or motor 10 is shown having a
housing 12 with an inlet port 14 and an outlet port 16. Within the
housing 12 are two intermeshing gears, 18 and 20. The first gear 18
is fixed to a rotatable shaft 22 and has a plurality of involute
gear teeth 24. Each gear tooth 24 has a top land 25 with a narrow
thickness. The other gear 20 is a shaftless gear having a plurality
of gear teeth 26, each gear tooth having a top land 27 which is
preferably at least twice as thick as the top lands on the first
gear 18. The shaftless gear 20, which preferably contains an
involute gear tooth profile, intermeshes with the first gear 18 and
is rotatable on a film of fluid in close proximity to an interior
surface 28 of the housing 12. As the gears 18 and 20 intermesh,
fluid is forced from the inlet port 14 around the periphery of the
two gears 18 and 20 and from the housing 12 through the outlet port
16.
In a conventional gear pump arrangement, power is delivered through
the rotatable shaft 22 making the gear 18 the drive gear and the
gear 20 the driven gear. In a standard gear motor arrangement, the
moving fluid acts as the driving force causing the two gears to
rotate thereby turning the rotatable shaft 22 which in turn is used
to operate another element, such as a drive belt.
Turning now to FIG. 2, a single gear tooth 26 is shown having a
thick top land 27, denoted as distance (a) and a normal face width
30, denoted as distance (b). The top land 27 is of such thickness
that the total thickness of all of the top lands 27 on the gear
teeth 26 of the shaftless gear 20 is approximately equal to between
30 and 50 percent of the circumference of the shaftless gear 20.
Preferably, the total thickness of all of the top lands 27 is equal
to approximately 40 percent of the circumference of the shaftless
gear 20. This extra thickness on the top lands 27 enables the
shaftless gear 20 to have a longer life expectancy because the
frictional wear between the shaftless gear 20 and the interior
surface 28 of the housing 12 is reduced. Furthermore, when the
total thickness of the top lands 27 of the gear teeth 26 equal
approximately 40 percent of the circumference of the shaftless gear
20, the shaftless gear 20 is supported by the gear teeth to about
the same degree as if a standard size gear shaft were coaxially
fixed through a central opening in the gear 20. By increasing the
support to the shaftless gear 20, the frictional wear between the
top lands 27 and the interior surface 28 of the housing 12 can be
reduced thereby increasing the life of the gear pump or motor 10.
With prolonged life, the need to replace the gear pump or motor 10
is substantially reduced thereby resulting in a cost savings to the
owner.
In FIG. 2, two edge chamfers 31 and 32 are formed on opposite sides
of the top land 27 and are aligned parallel to the central axis of
the shaftless gear 20. The edge chamfers 31 and 32 are inclined at
an angle (.phi.) of between about 10 and 30 degrees as measured
from the surface of the top land 27. These edge chamfers 31 and 32
assist in allowing a film of fluid to come between the top land 27
and the interior surface 28 of the housing 12 as the shaftless gear
20 is rotated therein. This feature of allowing the fluid to pass
over each top land 27 decreases the frictional wear and aids in
prolonging the life of the gear pump or motor 10. In addition to
the edge chamfers 31 and 32, an end chamfer 33 is also present
which is formed in the top land 27 perpendicular to the edge
chamfers 31 and 32. The end chamfer 33 is inclined at an angle
(.alpha.) of between about 30 and 50 degrees as measured from the
surface of the top land 27. This end chamfer 33 is beneficial in
the assembly process, particularly when the shaftless gear 20 is
placed into a circular bore or cavity which was machined into the
housing 12. When forming such a bore, it is difficult to construct
a sharp square corner between the cylindrical wall of the bore and
the bottom of the bore. Usually a slight radius is left which
prevents the shaftless gear 20 from seating flush against the
bottom of the bore. The end chamfer 33 allows the shaftless gear 20
to be inserted fully into this bore and also allows the shaftless
gear 20 to rotate more efficiently within the bore because
virtually no fluid will be trapped between the bottom of the bore
and the end of the shaftless gear 20. Without the presence of
trapped fluid, the efficiency of the gear pump or motor 10
increases.
Referring now to FIG. 3, an alternative configuration is shown for
a gear pump or motor 11. In this embodiment, two shaftless gears 20
and 21 mesh with a single gear 18 which is fixed to a rotatable
shaft 22. The presence of two intermeshing gear zones necessitates
two inlet ports 14 and 15 and two outlet ports 16 and 17 to be
formed in the housing 12. Such a gear pump or motor 11 would
facilitate the movement of a fluid in two directions. Although,
FIG. 3 specifically shows two shaftless gears intermeshing with a
gear 18 mounted on a rotatable shaft 22, it is conceivable that a
plurality of shaftless gears can be arranged to intermesh with a
single fixed gear 18. Such arrangements are contemplated by this
invention.
While the invention has been described in conjunction with two
specific embodiments, it is to be understood that many
alternatives, modifications and variations will be apparent to
those skilled in the art in light of the aforegoing description.
Accordingly, this invention is intended to embrace all such
alternatives, modifications and variations which fall within the
spirit and scope of the appended claims.
* * * * *